title: Long-term submergence at 3 degrees C of the turtle Chrysemys picta bellii in normoxic and severely hypoxic water. III. Effects of changes in ambient PO2 and subsequent air breathing.
abstract: Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0-21 in severely hypoxic water (PO2 = 0-5 mmHg), days 22-43 in aerated water (PO2 approximately 160 mmHg), and days 44-90 again in hypoxic water. From day 90 onward, the water was aerated and the turtles were allowed access to the air; water and air temperatures were maintained at 3 degrees C. Arterial blood samples were taken periodically and analysed for PO2, PCO2, pH, [Na+], [K+] [Cl-], [lactate-], [glucose] and haematocrit. Plasma [HCO3-] was calculated for all samples and total plasma calcium was measured on samples from two animals. Each exposure to low PO2 water caused progressive lactic acidosis and a transient respiratory acidosis with an accompanying fall in plasma [Cl-] and rise in plasma [K+] and [calcium]. During the intervening period in aerated water, blood pH recovered significantly (from 7.33 to 7.74 in 7 days), due primarily to a fall in PCO2 (from 23.5 to 10.6 mmHg), while [lactate-] remained unchanged (at about 50 mM), and [HCO-3] rose slightly. Plasma [K+] promptly returned to nearly normal values. When permitted to breathe on day 90, the three surviving turtles rapidly restored pH to normal by pronounced hyperventilation (PCO2 less than 5 mmHg). Metabolic acidosis, however, disappeared slowly with a t1/2 for [lactate-] and [HCO-3] restoration of about 2 weeks. We conclude that a wintering turtle can stabilize or even slightly improve its acid-base and ionic status by moving from an anoxic environment to well-oxygenated water. Further improvements can be gained by breathing air, but recovery proceeds at a very slow rate if the animal remains at 3 degrees C.
mesh_terms: D000064:Acclimatization; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002712:Chlorides / Q000097:blood; D003080:Cold Temperature; D006400:Hematocrit; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood*; D010313:Partial Pressure; D011188:Potassium / Q000097:blood; D012119:Respiration; D012964:Sodium / Q000097:blood; D014426:Turtles / Q000502:physiology*
chemical_list: D002712:Chlorides; D002245:Carbon Dioxide; D012964:Sodium; D011188:Potassium; D010100:Oxygen